The present invention relates to a system including a surgical apparatus for ultrasonically fragmenting, aspirating, and electrosurgically coagulating tissue at an operative site on a patient, and to an improvement in the electrical circuitry of such system, which improvement minimizes the RF current leakage.
The application of ultrasonically vibrating surgical devices for fragmenting and removing unwanted tissue with precision and safety has led to the development of valuable surgical procedures, and the use of ultrasonic aspirators for the fragmentation and surgical removal of tissue from a body has become well known. Initially, the technique of surgical aspiration was applied for the fragmentation and removal of cataract tissue as shown, for example, in U.S. Pat. Nos. 3,589,363 and 3,693,614; the disclosure in these patents and each of the other patents and documents mentioned herein are hereby incorporated by reference in their entirety. Later, such techniques were applied with significant success to neurosurgery and other surgical specialties where the application of ultrasonic energy through a small, handheld device for selectively removing tissue on a layer-by-layer basis with precise control has proven feasible.
Certain devices known in the art characteristically produce continuous vibrations having a substantially constant amplitude at a frequency of about twenty to about thirty KHz up to about forty to about fifty KHz. U.S. Pat. No. 3,589,363 describes one such device which is especially adapted for use in the removal of cataracts, while U.S. Pat. No. 4,063,557 describes a device suitable for removal of soft tissue which is particularly adapted for removing highly compliant elastic tissue mixed with blood. Such devices are continuously operative when the surgeon wishes to fragment and remove tissue, and generally operate under the control of a foot switch.
One known instrument for ultrasonically fragmenting tissue at an operative site and then aspirating the tissue particles and fluid away from the site is the CUSA model System 200 ultrasonic Aspirator which is manufactured and sold by Valleylab, Inc. of Stamford, Conn.; see also U.S. Pat. No. 4,827,911. When the longitudinally oscillating metallic tip in such an aspirator is brought into contact with tissue it gently, selectively and precisely fragments and removes the tissue. Some of the advantages of this unique surgical instrument are that there is little resulting damage to healthy tissue in a tumor removal procedure, blood vessels can be skeletonized, healing of tissue is promoted, no charring or tearing of margins of surrounding tissue results, only minimal pulling of healthy tissue is experienced, and excellent tactile feedback for selectively controlled tissue fragmentation and removal is provided.
Surgeons using the CUSA ultrasonic surgical instrument have indicated a desire for additional and improved capabilities for this instrument. In particular they have requested provisions for controlled penetration of capsular membranes without damage to the organs, precise and rapid removal of fibrous tissue structures such as in mucosal proctectomy procedures, and an increased rate of tissue fragmentation and removal. During many surgical procedures wherein ultrasonic fragmentation instruments have been employed additional instruments have been required for tissue cutting and hemostasis at the surgical site. Hemostasis is needed for example in desiccation techniques for deep coagulation to dry out large volumes of tissue and also in fulguration techniques for spray coagulation to dry out the surface of tissues. See, for example, U.S. Pat. No. 4,378,801. Often an electrosurgical pencil plugged into an electrosurgical unit for tissue cutting and hemostasis and a suction probe for aspiration of fluids and tissue particles are used. Since many surgical tools are thereby required at a single surgical site, the total surgical time is increased and efficiency decreased, as the surgeon must switch among different instruments. Also, undesirable amounts of blood are lost because of the time needed to switch from a cutting or fragmenting tool to a cauterizing instrument when bleeding is observed. Additionally, by simultaneously maintaining a plurality of surgical devices at the operative site the surgeon's field of view is reduced. Furthermore, due to the complexity of the procedures, false activation of the electrosurgical pencil, when not in use, can occur, thereby causing RF burning of the patient.
Accordingly, a need has arisen for an improved surgical procedure and apparatus which remedies these problems, and meets the above-expressed desires and needs of the surgeons.
The invention described and claimed in U.S. Pat. No. 4,931,047, the entire disclosure of which is incorporated hereby by reference, remedies these problems by incorporating RF coagulating and RF cutting capabilities to the vibratable tip of an ultrasonic fragmenting and aspiration device.
Thus, U.S. Pat. No. 4,931,047 provides a surgical apparatus for performing one or more surgical procedure at a surgical site on a patient comprising: a handpiece; a tool supported by said handpiece; said tool having a vibrating tool tip; an RF current means selectively operable for providing an RF current to said tool tip for allowing performance of an electrosurgical procedure at the surgical site; a vibrating means for ultrasonically vibrating said tool tip; said tool tip having a tip opening; said tool having a tool passageway therethrough communicating with said tip opening; and an aspirating means for applying a suction pressure on said tool passageway for aspirating tissue particles and fluid at the surgical site through said tip opening through said tool passageway and away from the surgical site, said RF current means including a switching means for switching the RF current provided to said tool tip to at least an RF cutting current during ultrasonic vibration.
Surprisingly, by using the above apparatus, the fragmentation and aspiration capabilities are actually enhanced by the delivery of RF energy to the fragmentation and aspiration tip. A switching mechanism conveniently accessible to the surgeon allows him during surgery and with the instrument tip at the surgical site to instantly switch among the application of no active function, one active function, or the simultaneous application of any combination of active functions of the instrument, thereby increasing the efficacy of the instrument and decreasing the time of the surgery. The bleeding which occurs during tissue fragmentation is more quickly and better controlled. There is also provision for controllable delivery of irrigation and cooling fluids to the surgical site.
The preferred switching means for switching the RF current to the tool tip in the apparatus of U.S. Pat. No. 4,931,047 includes a metallic electrical contact in the form of a thin metal strip which makes touching contact with the electrically conducting metal connecting member attached to the tool. Although this arrangement works well when the instrument is new, since the connecting member undergoes constant vibration when the instrument is in use, a certain amount of arcing is unavoidable and this causes erosion and/or build-up of an oxide coating on the metal contact strip or the connecting member or both, and such deterioration leads to increased electrical resistance and interference with the electronic circuitry, resulting in reduced efficiency.
Subsequently, it was found that an effective non-arcing electrical contact can be made and the above effect eliminated by making the electrical contact from the switch to the acoustic connecting member through a conductive O-ring connected to the switch module through a metal contact band. Since the O-ring is located around the acoustic member and is resilient enough to expand and contract with the ultrasonic vibrations, it remains in constant contact with the member and, therefore, is not subject to arcing. Thus, in an improvement described and claimed in U.S. Pat. No. 5,015,227, the entire disclosure of which is incorporated herein by reference, the switching means for switching the RF current to the tool tip comprises a switch module for selecting the RF current, an electrically conducting metal band connected to said switch module and an electrically conductive O-ring around said connecting member and in electrical contact with said metal band.
The apparatus disclosed in U.S. Pat. Nos. 4,931,047 and 5,015,227 provides hemostasis in combination with an ultrasonically vibrating surgical fragmentation instrument and aspirator. The apparatus is an effective surgical instrument which offers both a coagulation feature and an enhanced ability to fragment and aspirate tissue in a manner which reduces trauma to surrounding tissue.
However, it was discovered that the combination of RF electrical energy from a standard electrosurgical generator with the ultrasonic surgical aspirator might allow an unacceptable level of RF leakage current to leak to the patient or the surgeon holding the instrument.
It has now been found that unacceptable high levels of leakage current are reduced or eliminated by the inclusion in the output circuit of the generator of an impedance sensing network as hereinafter described.
Although various means are known in the art for changing the level of output power of an electrosurgical generator, for example, the switching arrangement disclosed in U.S. Pat. No. 4,827,927, the present invention provides the first application of impedance sensing and automatic power output controlling at high load impedance in a system incorporating ultrasonic fragmentation, aspiration and electrosurgical coagulation capabilities.